We study EGF receptor signaling in the early wing disc. This simple system is about 30 cells in a just hatched larva and grows to about 150 cells in two days. Our goal is to decipher the complete gene regulatory network that operates in this short period of time to specify the adult wing and body wall of the thorax. The simplicity and small size of the tissue make this a good system to analyze. We found that a paracrine Dpp (BMP/TGF-β) signal induces an EGF ligand called Vn (similar to the vertebrate neuregulins). Once Vn is induced it maintains its own expression in an autocrine loop. The finding that these conserved signaling pathways are operating leads to an expectation that the circuit in the wing will be used in other tissues and animals.
Flies have four EGF ligands—one called Vn (a neuregulin) and three that are like TGF-α (including Spi). Surprisingly, we found that any of the TGF-α ligands can replace Vn and rescue a mutant. We had to titrate the dose of the TFG-α ligand, because each is more potent that Vn. Our results support the idea that ligand identity is not critical, but that a certain level of signaling is required for the correct cellular response.
We have discovered genetic ways to generate Drosophila cell lines very efficiently. Expression of the Ras oncogene is one very powerful way to do this and we are using the cell lines to find new genes in the Ras pathway. We are using the cells to analyze tumor phenotypes. To enhance the range of possible experiments in Drosophila tissue culture we have developed a protocol to insert single transgenes into the same genomic site using site-specific recombination and a double drug selection.
Simcox Lab Members:
- Sathiya Maivannan
- Peter Lyon
- Molly Josifov
- Kristen Cornelius
- Nanki Hura
- Sandra Escobar
Paul L, Wang SH, Manivannan SN, Bonanno L, Lewis S, Austin CL, Simcox A. (2013) Dpp-induced Egfr signaling triggers postembryonic wing development in Drosophila. Proc Natl Acad Sci U S A. 110: 5058-63.
Simcox, A. (2012) Progress towards Drosophila epithelial cell culture. Epithelial Cells in Culture (Scott H Randell, editor). Second Edition: 1-11
Jonathon P. Butchar, Donna Cain, Sathiya N. Manivannan, Andrea D. McCue, Liana Bonanno, Sarah Halula, Sharon Truesdell, Christina L. Austin, Thomas L. Jacobsen, and Amanda Simcox (2012). New negative feedback regulators of Egfr signaling in Drosophila. Genetics 191:1213-1226.
Justiniano, S. Anne Mathew**, Sayan Mitra, Sathiya Manivannan, and Simcox, A. (2012). Loss of the Tumor Suppressor Pten Promotes Proliferation of Drosophila melanogaster Cells In Vitro and Gives Rise to Continuous Cell Lines. PLoS ONE.7(2): e31417. doi:10.1371/journal.pone.0031417.
Leonardi J, Fernandez-Valdivia R, Li YD, Simcox AA, Jafar-Nejad H (2011) Multiple O-glucosylation sites on Notch function as a buffer against temperature-dependent loss of signaling. Development 138: 3569-3578.
Simcox, A., Austin, C., Jacobsen, T.J., Jafar-Nejad, H. (2008) Drosophila embryonic ‘fibroblasts’: extending mutant analysis in vitro. Fly 2, 306-9.
Simcox, A., Mitra, S., Truesdell, S., Paul, L., Chen, T., Butchar, J.P., Justiniano, S. (2008) Efficient genetic method for establishing Drosophila cell lines unlocks the potential to create lines of specific genotypes. PLoS Genetics4:8 e1000142.
- The role of oncogenes, tumor suppressors and Egfr signaling in growth control and development in Drosophila